Method for purifying acrylamide alkyl sulfonic acid

ABSTRACT

A method for purifying acrylamide alkyl sulfonic acid comprises: (1) making a material A evenly mixed and contacted with a solvent C, an amount of the material A exceeding a solubility of the material A in the solvent C under the condition where the material A is located, therefore the material A is not completely dissolved by the solvent C; (2) keeping the material A even mixed and contacted with the solvent C for at least 5 minutes; (3) performing a solid-liquid separation to obtain a solid, namely, a purified product B with impurities reduced. In the purifying method according to the invention, the material does not need to be completely dissolved, therefore less solvent is used, and the steps of dissolving the material by increasing temperature, separating out by decreasing temperature or removing the solvent are eliminated, so cost is reduced, efficiency is improved, and operations are simplified.

TECHNICAL FIELD

The present invention relates to a purifying method, and particularly toa method for purifying acrylamide alkyl sulfonic acid.

BACKGROUND ART

Acrylamide alkyl sulfonic acid and analogues thereof, mainly as aco-monomer and homo-monomer, are widely used in many industries. In somesituations where very high degree of polymerization is demanded, theproduct directly synthesized may still need to be refined to furtherimprove the quality. Many documents, e.g. U.S. Pat. No. 4,337,215, andactual productions relate to the recrystallization purification ofacrylamide alkyl sulfonic acid. But the solid added is completelydissolved in all of these refining processes in the prior art, forexample, the solid is completely dissolved by increasing thetemperature, and then the solid is re-separated out through the methodssuch as reducing the solvent by decreasing the temperature of the systemor by evaporation, rather than intending to use significantly excessivesolid. Moreover, all of these methods mainly use organic solvents, suchas acetic acid or acetic acid added with a small amount of water, whileit is hard to directly use pure water. The advantage of these methods isthat the refined product obtained has very good quality, but thedisadvantages are high cost, low efficiency, and complex process, etc.

DISCLOSURE OF THE INVENTION

The technical problem to be solved by the present invention is toprovide a method for purifying acrylamide alkyl sulfonic acid, which haslow cost, high efficiency, and simple and easy operations.

A method for purifying acrylamide alkyl sulfonic acid comprises thesteps of:

(1) making a material A evenly mixed and contacted with a solvent C,wherein the material A comprises at least one acrylamide alkyl sulfonicacid compound represented by the following general formula:

in which R¹ and R² are hydrogen and/or alkyl groups containing 1 to 20carbons, wherein an amount of the material A exceeds the solubility ofthe material A in the solvent C under a condition where the material Ais located, so that the material A is not completely dissolved by thesolvent C;

(2) keeping the material A even mixed and contacted with the solvent Cfor at least 5 minutes;

(3) performing a solid-liquid separation, wherein because the liquidremoved upon separation takes away a portion of impurities dissolved inthe liquid, the solid obtained by separation has a reduced amount ofimpurities, obtaining a purified product B.

In the method for purifying acrylamide alkyl sulfonic acid of thepresent invention, Step (3) is in either of the following two cases:

1) performing a solid-liquid separation, wherein the solid obtained isnot subjected to a drying process, or is subjected to a drying processat or below 50° C., to obtain the purified product B with a watercontent of greater than or equal to 1%;

2) performing a solid-liquid separation, wherein the solid obtained issubjected to a drying process at or above 50° C., to obtain the purifiedproduct B with a water content of less than 1%.

In the method for purifying acrylamide alkyl sulfonic acid of thepresent invention, the liquid obtained by the solid-liquid separation isa mother liquor, the solvent C includes the mother liquor obtained inthe previous purification or a solution from other sources containingthe material A, with the content of the mother liquor or solution of0˜100%.

In the method for purifying acrylamide alkyl sulfonic acid of thepresent invention, the solvent C comprises at least one selected fromthe group consisting of the following solvents: water, acid containing1-8 carbons, amide containing 1-8 carbons, alcohol containing 1-8carbons, ketone containing 1-8 carbons, ether containing 1-8 carbons,ester containing 1-8 carbons, alkane containing 1-8 carbons, andhalogenated hydrocarbon containing 1-8 carbons.

In the method for purifying acrylamide alkyl sulfonic acid of thepresent invention, the amount of the added material A exceeding thesolubility of the material A in the solvent C is 0.01-10 time of thesolubility, with the solubility under the condition where the materialis located.

In the method for purifying acrylamide alkyl sulfonic acid of thepresent invention, the temperature of the whole system is controlledbetween −20° C. and 120° C. during the purifying process, and thetemperature is controlled as constant or changed between differenttemperatures.

In the method for purifying acrylamide alkyl sulfonic acid of thepresent invention, the material A is contacted with the solvent C for0.5-48 hours.

In the method for purifying acrylamide alkyl sulfonic acid of thepresent invention, the amount of the added material A exceeding thesolubility of the material A in the solvent C is 0.5-3 time of thesolubility, with the solubility under the condition where the materialis located; the temperature of the whole system is controlled 0° C. to25° C. during the purifying process, and the material A is contactedwith the solvent C for 0.5-5 hours.

In the method for purifying acrylamide alkyl sulfonic acid of thepresent invention, the method further comprises adding a polymerizationinhibitor until a concentration of the polymerization inhibitor reaches0 mg/kg˜1000 mg/kg and/or feeding oxygen or air, aiming at reducing therisk of polymerization.

The method for purifying acrylamide alkyl sulfonic acid of the presentinvention comprises steps of:

evenly blending acrylamide methyl sulfonic acid, in which both R¹ and R²are methyl groups in the general formula, with water, and then slowlystirring or allowing the mixture to stand for 0.5-3 hours, with theamount of the added acrylamide methyl sulfonic acid being 1-4 times thesolubility in water under an environment where the acrylamide methylsulfonic acid is located, removing water by filtration or centrifugationto obtain a solid, wherein the purified product obtained is one of thefollowing:

(1) the solid obtained, namely, the product, which is not subjected to adrying process, or subjected to a drying process at or below 50° C.,with a water content of greater than or equal to 1%;

(2) the solid obtained, which is subjected to a drying process at orabove 50° C. to obtain a product with a water content of less than 1%.

The present invention is different from the prior art in that: in thepresent invention, after an excessive amount of the material A is incontact with the solvent C for a relatively long period of time, thesolid-liquid separation is performed to obtain the solid with a reducedamount of impurities, and a wet product or a dried non-wet product withimproved purity is obtained directly. Compared with the conventionalmethod in which the material is dissolved completely, and thenre-separating out by decreasing the temperature or removing the solventto obtain a purified product by separation, since the material does notneed to be completely dissolved, less solvent can be used, and the stepsof dissolving the material by increasing the temperature, and separatingout by decreasing the temperature or removing the solvent and the likeare eliminated, so that the cost is reduced, the efficiency is improved,and the operations are simplified.

Below, the method of the present invention is further described incombination with specific examples.

DETAILED DESCRIPTION OF EMBODIMENTS Example 1

A method for purifying acrylamide alkyl sulfonic acid comprised thefollowing steps:

making a material A evenly mixed and in contact with a solvent C,wherein the material A is acrylamide methyl sulfonic acid with both R¹and R² being methyl groups in the above-mentioned general formula, thesolvent C is water, and the amount of the added material A exceeding thesolubility in water under the condition where the material is located istwice the solubility, and the temperature of the whole system iscontrolled at 10° C. during the purifying process, the temperature iscontrolled as constant; making the material A in contact with thesolvent C for 3 hours; performing a solid-liquid separation in afiltration manner to obtain a wet material of a purified product B, andto obtain the purified dry product B after drying the wet material.

Example 2

A method for purifying acrylamide alkyl sulfonic acid comprised thefollowing steps:

making a material A evenly mixed and contacted with a solvent C, whereinthe material A is acrylamide methyl sulfonic acid with both R¹ and R²being methyl groups in the above-mentioned general formula, the solventC is water, the solvent C comprises a mother liquor of a content of 50%obtained from the previous purification, and the amount of the addedmaterial A exceeding the solubility in water under the condition wherethe material is located is four times of the solubility, the temperatureof the whole system is controlled at 0° C.-25° C. during the purifyingprocess, the temperature is controlled as being changed to differenttemperatures in the range of 0° C.-25° C; adding a polymerizationinhibitor into the system, the concentration as 1000 mg/kg; making thematerial A contacted with the solvent C for 6 hours; performing asolid-liquid separation in a centrifugation manner to obtain a wetmaterial of a purified product B.

Example 3

A method for purifying acrylamide alkyl sulfonic acid comprised thefollowing steps:

making a material A evenly mixed and contacted with a solvent C, whereinthe material A is acrylamide methyl sulfonic acid with both R¹ and R²being methyl groups in the above-mentioned general formula, the solventC is a mother liquor obtained in the previous purification, and theamount of the added material A exceeding the solubility in water underthe condition where the material is located is 0.1 times of thesolubility, the temperature of the whole system is controlled at 25° C.during the purifying process, the temperature is controlled as constant;feeding oxygen into the system; making the material A contacted with thesolvent C for 0.2 hours; performing a solid-liquid separation in afiltration manner to obtain a wet material of a purified product B, andto obtain the purified dry product B after drying the wet material.

Example 4

A method for purifying acrylamide alkyl sulfonic acid comprised thefollowing steps:

making a material A evenly mixed and contacted with a solvent C, whereinthe material A is acrylamide methyl sulfonic acid with both R¹ and R²being methyl groups in the above-mentioned general formula, the solventC is acetic acid with water of 50%, and the amount of the added materialA exceeding the solubility in the solvent C under the condition wherethe material is located is six times of the solubility, the temperatureof the whole system is controlled between −15° C. and 90° C. during thepurifying process, the temperature is controlled as being changed todifferent temperatures in the range of −15° C. to 90° C.; feeding airinto the reaction system; making the material A contacted with thesolvent C for 1 hour; performing a solid-liquid separation in afiltration manner to obtain a wet material of a purified product B.

Example 5

A method for purifying acrylamide alkyl sulfonic acid comprised thefollowing steps:

making a material A evenly mixed and contacted with a solvent C, whereinthe material A is acrylamide methyl sulfonic acid with R¹ being an ethylgroup and R² being an alkyl group having 20 carbons in theabove-mentioned general formula, the solvent C is alcohol containing 1-8carbons, the solvent C comprises other solution of a content of 60%,with said other solution containing the material A, the amount of theadded material A exceeding the solubility in the solvent C under acondition where the material is located is 5 times of the solubility,the temperature of the whole system is controlled at 45° C. during thepurifying process, the temperature is controlled as constant; making thematerial A contacted with the solvent C for 24 hours; performing asolid-liquid separation in a centrifugation manner to obtain a wetmaterial of a purified product B, and to obtain the purified dry productB after drying the wet material.

Example 6

A method for purifying acrylamide alkyl sulfonic acid comprised thefollowing steps:

making a material A evenly mixed and contacted with a solvent C, whereinthe material A is acrylamide methyl sulfonic acid with R¹ being an alkylgroup containing 15 carbons and R² being an alkyl group containing 8carbons in the above-mentioned general formula, the solvent C isacetone, and the amount of the added material A exceeding the solubilityin the solvent C under the condition where the material is located istwice the solubility, the temperature of the whole system is controlledat 5° C.-30° C. during the purifying process, the temperature iscontrolled as being changed to different temperatures in the range of 5°C.-30° C.; adding a polymerization inhibitor into the system, theconcentration of the polymerization inhibitor as 50 mg/kg; making thematerial A contacted with the solvent C for 48 hours; performing asolid-liquid separation in a filtration manner to obtain a wet materialof a purified product B.

Example 7

A method for purifying acrylamide alkyl sulfonic acid comprised thefollowing steps:

making a material A evenly mixed and contacted with a solvent C, whereinthe material A is acrylamide methyl sulfonic acid with R¹ being H and R²being an alkyl group containing 12 carbons in the above-mentionedgeneral formula, the solvent C is dimethylformamide containing thematerial A, and the amount of the added material A exceeding thesolubility in the solvent C under the condition where the material islocated is four times of the solubility, the temperature of the wholesystem is controlled at 70° C. during the purifying process, thetemperature is controlled as constant; making the material A contactedwith the solvent C for 5 minutes; performing a solid-liquid separationin a filtration manner to obtain a wet material of a purified product B,and to obtain the purified dry product B after drying the wet material.

Example 8

A method for purifying acrylamide alkyl sulfonic acid comprised thefollowing steps:

making a material A evenly mixed and contacted with a solvent C, whereinthe material A is acrylamide methyl sulfonic acid with R¹ being an alkylgroup containing 15 carbons and R² being an alkyl group containing 2carbons in the above-mentioned general formula, the solvent C is amixture containing water and acetone and methyl ethyl ether andtrichloromethane, and the amount of the added material A exceeding thesolubility in water under the condition where the material is located isthree times of the solubility, the temperature of the whole system iscontrolled at 10° C. to 30° C. during the purifying process, thetemperature is controlled as being changed to different temperatures inthe range of 10° C. to 30° C., making the material A contacted with thesolvent C for 0.5 hours; performing a solid-liquid separation in acentrifugation manner to obtain a wet material of a purified product B.

Example 9

A method for purifying acrylamide alkyl sulfonic acid comprised thefollowing steps:

making 1500 g of a material A evenly mixed and contacted with 500 g ofwater, wherein the material A is acrylamide methyl sulfonic acid withboth R¹ and R² being methyl groups in the above-mentioned generalformula, and the temperature of the whole system is controlled at 15° C.during the purifying process; making the material A contacted with waterfor 1 hour; performing a solid-liquid separation in a filtration mannerto obtain a wet material of a purified product B.

The examples described above are merely to describe the preferredembodiments of the present invention but not to limit the scope of thepresent invention. For an ordinary person skilled in the art, variousalterations and improvements made to the technical solutions of thepresent invention, without departing from the design spirit of thepresent invention, should be fallen into the scope of protection definedin the Claims of the present invention.

INDUSTRIAL APPLICABILITY

In the method for purifying acrylamide alkyl sulfonic acid of thepresent invention, the material does not need to be completelydissolved, and less solvent can be used, and the steps of dissolving thematerials by increasing the temperature, and separating out thematerials by decreasing the temperature or removing the solvent and thelike are eliminated, thus it is much more simplified than theconventional method of recrystallization and purification, and also canobtain the product having better quality than that obtained through theordinary simple washing method; in particular, due to the property ofinstability of the double bond of acrylamide alkyl sulfonic acid whenheated in water, the solvents such as acetic acid or methanol containinga certain amount of water are mainly used currently in industry forrefining, therefore, the cost is high, and the pollution is severe.However, as the process of heating and increasing the temperature andthe like are eliminated in the method of the present invention, watercan be used directly as solvent for refining, as a result, the cost isgreatly reduced, the efficiency is significantly improved, and theoperations are considerably simplified; the method according to thepresent invention is environmentally-friendly and energy-saving, safeand reliable, and has a great market prospect and strong industrialapplicability.

1. A method for purifying acrylamide alkyl sulfonic acid, wherein themethod comprises steps of: (a) making a material A evenly mixed andcontacted with a solvent C, the material A comprising at least oneacrylamide alkyl sulfonic acid compound represented by the followinggeneral formula:

in which R¹ and R² are hydrogen and/or an alkyl group containing 1 to 20carbons, and an amount of the material A exceeds a solubility of thematerial A in the solvent C under a condition where the material A islocated, so that the material A is not completely dissolved by thesolvent C; (b) keeping the material A even mixed and contacted with thesolvent C for at least 5 minutes; (c) performing a solid-liquidseparation to obtain a solid, namely, a purified product B, wherein theproduct B is the purified material A, wherein the method does notinclude steps of dissolving the material A by increasing temperature andof re-separating out by decreasing temperature or removing the solvent.2. The method for purifying acrylamide alkyl sulfonic acid according toclaim 1, wherein Step (3) is in either of the following two cases: i)performing the solid-liquid separation, wherein the solid obtained isnot subjected to a drying process, or is subjected to a drying processat or below 50° C., to obtain the purified product B with a watercontent of greater than or equal to 1%; ii) performing the solid-liquidseparation, wherein the solid obtained is subjected to a drying processat or above 50° C., to obtain the purified product B with a watercontent of less than 1%.
 3. The method for purifying acrylamide alkylsulfonic acid according to claim 2, wherein a liquid obtained by thesolid-liquid separation is a mother liquor, and the solvent C comprisesa mother liquor obtained in the previous purification or a solution fromother source with the solution containing the material A with a contentof the comprised mother liquor or the solution being 0˜100%.
 4. Themethod for purifying acrylamide alkyl sulfonic acid according to claim2, wherein the solvent C includes at least one selected from the groupconsisting of the following solvents: water, acid containing 1-8carbons, amide containing 1-8 carbons, alcohol containing 1-8 carbons,ketone containing 1-8 carbons, ether containing 1-8 carbons, estercontaining 1-8 carbons, alkane containing 1-8 carbons, and halogenatedhydrocarbon containing 1-8 carbons.
 5. The method for purifyingacrylamide alkyl sulfonic acid according to claim 4, wherein an amountof the added material A exceeding the solubility of the material A inthe solvent C under a condition where the material A is located is0.01-10 times of the solubility.
 6. The method for purifying acrylamidealkyl sulfonic acid according to claim 5, wherein a temperature of thewhole system is controlled between −20° C. and 120° C. during apurifying process, the temperature is controlled as constant or changedto different temperatures.
 7. The method for purifying acrylamide alkylsulfonic acid according to claim 6, wherein the material A is contactedwith the solvent C for 0.5-48 hours.
 8. The method for purifyingacrylamide alkyl sulfonic acid according to claim 7, wherein the amountof the added material A exceeding a solubility of the material A in thesolvent C under a condition where the material A is located is 0.5-3times of the solubility; the temperature of the whole system iscontrolled between 0° C. and 25° C. during the purifying process, andthe material A is contacted with the solvent C for 0.5-5 hours.
 9. Themethod for purifying acrylamide alkyl sulfonic acid according to claim5, wherein the method further comprises: adding a polymerizationinhibitor until a concentration of the polymerization inhibitor reaches0 mg/kg˜1000 mg/kg, and/or feeding oxygen or air.
 10. The method forpurifying acrylamide alkyl sulfonic acid according to claim 9, whereinthe method comprises steps of: evenly blending acrylamide methylsulfonic acid, in which both R¹ and R² are methyl groups in the generalformula, with water to obtain a mixture, then slowly stirring orallowing the mixture to stand for 0.5-3 hours, with an amount of theadded acrylamide methyl sulfonic acid being 1-4 times the solubility ofthe acrylamide methyl sulfonic acid in water under an environment wherethe acrylamide methyl sulfonic acid is located, removing water byfiltration or centrifugation to obtain a solid, wherein the purifiedproduct obtained is one of the following: (i) the solid obtained,namely, a product, which is not subjected to a drying process, or issubjected to a drying process at or below 50° C., with a water contentof greater than or equal to 1%; (ii) the solid obtained, which issubjected to a drying process at or above 50° C. to obtain a productwith a water content of less than 1%.